Certain drugs or medicaments (those terms being used interchangeably herein) are preferably provided in powder or dry form (such as a lyophilized form), and require reconstitution prior to administration. Lyophilized drugs, for example, typically are supplied in a freeze-dried form that needs to be mixed with a diluent to reconstitute the substance into a form that is suitable for injection. Medicaments may also be provided in other dry or powder form that require reconstitution.
In addition, drugs may be provided as multipart systems which require mix ng prior to administration. For example, one or more liquid (e.g., flowable (slurry or liquid)) components, and/or dry (e.g., powdered or granular) components may be provided in a drug container or delivery device which require mixing prior to administration. The components can be mixed and used to form various administratable drugs, such as insulin.
It is known in the prior art to mix substances using a syringe and a vial. Typically, a flowable material is provided in the syringe which is intended for mixing with a secondary component accommodated in the vial. The septum of the vial is caused t be pierced by the needle of the syringe with the flowable material being urged from the syringe under force of movement of the plunger. With the flowable material in the vial, the vial is agitated so as to cause mixing of the flowable material and the secondary component. Once mixed, the mixed substance is then aspirated into a new syringe. The syringe may then be used for administration of the mixed substance. This arrangement, however, has some drawbacks. Dose size, where less than the entire dose of the mixed substance is required, may be difficult to control accurately. In addition, a syringe is a one-time use device which can not be used for multiple doses over time. Anew syringe is required for each dose administration. Syringes arc difficult to use for self-administration.
Transfer sets, which include a fixturing device, have been developed to facilitate fluid transfer between components in obtaining mixing thereof.
Pen injectors permit good dose-size control, multiple doses over time and are well-suited for self-administration. To achieve mixing of substances in pen injectors, prior art devices have been developed that provide a wet component (e.g., liquid) and a dry component (e.g., powder) in separate chambers of a common container with the container being configured to permit the flow of the wet component to the dry component to cause mixing thereof in preparing an administratable solution for injection. U.S. Pat. No. 4,874,381 to Vetter is directed to an injector having a barrel configured for mixing, while U.S. Pat. No. 4,968,299 to Ahlstrand et al. is directed to a drug cartridge having a barrel configured for mixing. Both Vetter et al. and Ahlstrand et al. disclose typical configurations for mixing where a bypass channel is formed in the barrel of the device. These devices also suffer drawbacks. These containers must be specifically configured for mixing and, typically, are more expensive to manufacture than conventional containers (cartridges, injector barrels). In addition, these containers typically have a substantial amount of wasted dead space (e.g., volume of wasted dead space may be four to five times the volume of the accommodated substance). The excess wasted dead space results in larger-size containers, which may be less convenient to handle and more inaccurate for dosing purposes.